Apr 14 2009
Fun with Stalactites and Stalagmites
Have you ever explored a cave and wondered what the ‘things’ are that grow from the ceiling of the cave downward, and upward from the floor. These are called “Stalactites” and Stalagmites”. Ok, which is which – a stalactite grows from the ceiling down and the stalagmite grows up from the floor.
Stalactites and Stalagmites form when water seeps its way through the ceiling of the cave and drips, when it drips, it leaves behind a mineral formation, which is the stalactite and as the water hits the floor, a mineral deposit from the water begins to build up over time, thus the stalagmite is formed. When a stalactite and a stalagmite touch, they form a column. A cave that is rich in limestone is one where these formations are most often found. There are just over 50 minerals that may cause the formation of stalactites and stalagmites in caves. They have a very slow rate of growth - 0.00028–0.037 in/yr.
Now that we have had a quick lesson on what they are, let us enjoy a fun science experiment using baking soda to create your own. For this exercise, you will need to round up the following:
• 2 glasses or jars
• 1 plate or saucer
• 1 spoon
• 2 paper clips
• Hot tap water
• 1 piece of yarn about 3 feet (cotton or wool, un colored if possible)
• Baking soda
• Food coloring if you desire to color your creation.
Fold the piece of yarn in half, then in half again, then tightly twist it. Attach the paper clips to each end of the yarn – this will support the yarn while it rests in the liquid. Next, position the glasses at opposite sides with the bowl or saucer in the center, then place your yarn over the glasses with the end in each glass, and allow it to sag slightly over the saucer or bowl. Next you will create your forming solution. Mix baking soda in hot tap water (add food coloring if you wish), saturating it to the point where you are not able to dissolve any more baking soda in the water. (The amount of mixture you will make depends on the size glasses you use – you will fill the glasses with the solution).
Pour the liquid into each glass – filling it right up. The liquid will begin to be absorbed by the yarn and will make its way through as time goes on – after a period of time you will begin to notice stalactites starting to form – going down towards the plate (watch the plate or bowl, it might begin to pool with water, keep it empty). The rate of growth of your creation will vary depending upon humidity, temperature, rate of evaporation, and the mixture. Have fun; try different variations of the mixture and even different types of yarn or string. Enjoy! Recipe from About.com and rate of growth statistic from Wikipedia.
That looks like fun! I have visited many caves, and have probably been told the difference and never would have remembered!